1. Field of the Invention
The present invention relates to an elevator control apparatus utilizing a power storage unit.
2. Description of the Related Art
A conventional elevator control apparatus will be described with reference to an accompanying drawing. FIG. 19 shows a construction of a conventional elevator control apparatus disclosed, for example, under a title of xe2x80x9cRedesigned medium-to-low speed passenger elevator, Grandyxe2x80x9d on page 9 of Mitsubishi Denki Giho (written by Ando, Kimura, and Mori, Vol. 70, No. 11 issued in 1996).
The conventional elevator control apparatus shown in FIG. 19 includes a commercial three-phase AC power source 1, a motor 2, such as an induction motor IM, a hoisting machine 3, a rope 4, an elevator car 5, a counterweight 6, an encoder 7, a controller 8, a converter 9 formed of a diode or the like, a capacitor 10, a current detector 11, such as a current transformer (CT), an inverter 12, an inverter control circuit 13, a gate drive circuit 14, a regenerative resistor 15, and a switching means 16, such as an IGBT.
An operation of the aforesaid conventional elevator control apparatus will now be described with reference to the drawing.
The hoisting machine 3 is driven by the motor 2 to move the elevator car 5 and the counterweight 6 connected to both ends of the rope 4, thereby carrying passengers in the car to a predetermined floor.
The converter 9 rectifies AC power supplied from the commercial power source 1 to convert it into DC power, which is stored in the capacitor 10. The DC power is converted into AC power of a variable voltage and a variable frequency by the inverter 12.
The controller 8 controls starts and stops of the elevator and also creates commands regarding start and stop positions and speed. Based on a speed command supplied by the controller 8, the inverter control circuit 13 rotationally drives the motor 2 by reflecting current feedback from the current detector 11 and speed feedback from the encoder 7 mounted on the hoisting machine 3, thereby implementing the position and speed control of the elevator. At this time, the inverter control circuit 13 controls output voltages and frequencies of the inverter 12 via the gate drive circuit 14.
The counterweight 6 of the elevator is set such that it is balanced when the car 5 is loaded with a moderate number of passengers. For example, when the elevator travels in a balanced state, it is possible to increase the speed of the elevator while consuming electric power in an acceleration mode, and to turn accumulated speed energy back into electric power in a deceleration mode. In typical elevators, however, the regenerative electric power is consumed by being converted into heat energy by the regenerative resistor 15 by controlling the switching means 16.
The conventional elevator control apparatus described above operates the elevator by constantly supplying electric power from the commercial power source. This has been posing a problem in that the electric power generated during a regenerative mode of the elevator is thermally consumed mainly by the regenerative resistor rather than being effectively used.
The present invention has been made with a view toward solving the foregoing problem, and it is an object of the present invention to provide an elevator control apparatus that permits energy saving by effectively utilizing electric power generated during a regenerative mode of an elevator.
To this end, according to one aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller; a charge/discharge control circuit which conducts control by changing charge current, which is to be supplied to the power storage unit, based on regenerative electric power, and issues a drive signal for charging the power storage unit with the regenerative electric power if required power of the elevator is negative, that is, if the regenerative electric power is available; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset voltage that is not less than a voltage obtained by rectifying the AC power, and issues a drive signal for charging the power storage unit with the regenerative electric power if required power of the elevator is negative, that is, if the regenerative electric power is available; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to yet another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller and issuing a regenerative operation signal if the required power is negative; a charge/discharge control circuit that starts charge control of regenerative electric power and issues a drive signal for charging the power storage unit with the regenerative electric power upon receipt of the regenerative operation signal; and a charge/discharge circuit for starting charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to still another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that stops charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power upon receipt of an elevator stop signal from the controller; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that starts charge control of regenerative electric power and issues a drive signal for charging the power storage unit with the regenerative electric power when a bus voltage between the converter and the inverter reaches a preset predetermined voltage that is higher than a voltage obtained by rectifying the AC power; and a charge/discharge circuit for starting charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that carries out control such that a bus voltage between the converter and the inverter stays constant at a present voltage that is not less than a voltage obtained by rectifying the AC power, and stops the charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power when charge current is controlled until it reaches zero; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that controls a charge current supplied to the power storage unit at a constant present predetermined current value and issues a drive signal for charging the power storage unit with the regenerative electric power at the constant current; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that stops charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power when a bus voltage between the converter and the inverter reaches a preset predetermined voltage that is higher than a voltage obtained by rectifying the AC power; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that controls charge current supplied to the power storage unit at a plurality of present predetermined constant current values in steps based on the bus voltage between the converter and the inverter, and issues a drive signal for charging the power storage unit with regenerative electric power at constant current; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal.
According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage and that, when charge current supplied to the power storage unit reaches a preset predetermined upper limit value, the charge current stays at the upper limit value, and issues a drive signal for charging the power storage device with regenerative electric power; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal.
In a preferred form of the invention, when the charge current supplied to the power storage unit reaches the predetermined upper limited value, and if the bus voltage exceeds a preset second predetermined voltage while charging the power storage unit at the upper limit value is being continued, then the charge/discharge control circuit causes a part of the regenerative electric power to be thermally consumed by a resistor.
According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage, issues a first drive signal for charging the power storage unit with the regenerative electric power control, and stops charge control of the regenerative electric power and issues a second drive signal for stopping charging the power storage unit with the regenerative electric power when a voltage of the power storage unit reaches a preset predetermined upper limit value; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the first drive signal and for stopping charging the power storage unit with the regenerative electric power in accordance with the second drive signal.
According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage, issues a drive signal for charging the power storage unit with regenerative electric power, and carries out control such that the charge current supplied to the power storage unit reaches a predetermined upper limit value and issues a drive signal for charging the power storage unit with regenerative electric power when a voltage of the power storage unit reaches a preset predetermined voltage; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signals.
In a preferred form of the invention, when the voltage of the power storage unit reaches the preset predetermined voltage, and if the bus voltage exceeds a preset second predetermined voltage while charging the power storage unit at the upper limit value is being continued, then the charge/discharge control circuit causes a part of the regenerative electric power to be thermally consumed by a resistor.